Field of the Invention
The present invention relates to an apparatus that operates with a unit mounted therein, and more particularly to an apparatus that verifies the validity of the unit by verifying data held by the unit.
Description of the Related Art
Image forming apparatuses operate with external units that are detachable from the main body of the image forming apparatus, such as process cartridges or other replaceable units, mounted therein. Some of these external units are provided with a memory that holds identification information for identifying the external unit and control information that controls the operations of the image forming apparatus when the external unit is mounted. Here, the memory is an electronic device, and it is foreseen that invalid control information will be written thereto due to communication errors and the like that occur when the memory is written. When an external unit to which invalid control information has been written is mounted in the main body of an image forming apparatus and used, there is a risk of the image forming apparatus being adversely affected.
Authentication technologies are utilized in order to distinguish the validity of control information. Authentication technologies include message authentication code technologies based on shared key encryption and digital certificate technologies based on public key encryption. As a message authentication code technology, for example, the technology described in ISO 9797-1 is used. Also, ISO 9796-2 discloses a configuration that generates signature data using a secret key, and performs authentication using a public key that is paired with the secret key. Also, Japanese Patent Laid-Open No. 2005-167977 discloses a configuration for verifying the validity of products.
When an external unit is mounted, it is sought to quickly detect whether the external unit has been erroneously inserted. It is also necessary to verify whether information in the memory of the mounted external unit is valid. In other words, it is necessary to verify whether the mounted external unit is valid. Here, an external unit being valid means that the external unit is a genuine product and has not been erroneously inserted.